An optical transceiver is a core apparatus which converts an electrical signal, such as video, audio, and data, into an optical signal or reversely converts the optical signal into the electrical signal in an optical communication system such as an optical repeater to be able to provide communication between systems.
As the optical transceiver used in an optical repeater for wireless mobile communication in the beginning, a basic optical transceiver using a laser diode (LD) having a wavelength of 1310 nm and 1550 nm has been mainly used. However, for advancement and more efficient operation of the optical repeater, the optical transceiver is being developed to have a structure of using a plurality of coarse wavelength division multiplexing (CWDM) LDs, such as 1490 nm, 1510 nm, 1530 nm, and 1570 nm in addition to 1310 nm and 1550 nm.
For the use of the plurality of CWDM LDs, there is a need to use a more precise CWDM wavelength filter to reduce interference between LDs having a proximity wavelength.
However, the use of the CWDM filter may cause several problems. As a representative example of the problems, the optical signal of the LD is filtered within an operation temperature of equipment, thereby reducing performance of the optical communication system or in the worst case, stopping the operation thereof.
A general laser diode used in the existing optical transceiver has many limitations in a wavelength use region since the wavelength is changed with the change in temperature of ambient environment. In particular, in the case of a low-density coarse wavelength division multiplexing (CWDM) optical module, when a general uncooled laser diode is used in a temperature range of −40° C. to +85° C. (generally, temperature range of 0° C. to +70° C.), the wavelength of the laser diode (LD) is changed as much as about 0.1 nm/° C. with the change in temperature, thereby causing the wavelength interference between the channels.
To remove the interference effect, the uncooled laser diode may not accept the change in a maximum of wavelength of +/−6.5 nm from central wavelengths which are referenced for each wavelength channel. Since the uncooled laser diode limits the use of laser, the uncooled laser diode may not be mass-produced and the price thereof may rise.
The problem may be resolved by using a cooled laser diode using a temperature electric cooler (TEC). As an example of the cooled laser diode using the TEC, there may be Korean Patent Laid-Open Publication No. 10-2006-0111760 (Apparatus For Controlling Use Temperature Of Optical Module Using Uncooled Laser Diode).
In this case, however, when the uncooled laser diode is applied to the low-density coarse wavelength division multiplexing (CWDM) optical module, the price of equipment rises due to addition of a circuit for controlling temperature, rising cost of raw materials of TEC, difficulty in an assembly, and the like, such that it is difficult to commercialize the uncooled laser diode.
Further, when using a general heater, the uncooled laser diode additionally requires a control circuit for sensing temperature and controlling the temperature so as to control the heater, such that a circuit may be complicated, and additionally requires a PCB layer for the control circuit, such that the difficulty in an assembly may be increased and a considerable large space may be required.